Follow the standard trail like you are going to Sentinel Buttress but instead of taking the right to go up the hill continue on and down the large trail a little ways and keep an eye out for a small trail on the right (little ways downhill past the amphitheater sign). It will not be marked.

Follow this trail and you will pass a single boulder on your right. (warmup boulder with mostly easy stuff) Continue down the trail and it will curve towards the right sorta down hill. The next boulder you end at should be triple XXX boulder.